Conventionally, there has been a proposed method of recovering a useful element such as a rare earth element from scraps of an iron-based alloy material. For example, Japanese Patent Laying-Open No. 03-207825 (which will be hereinafter referred to as PTD 1) discloses a method of separating and recovering a rare earth element by dissolving rare-earth magnet scraps in a nitric acid-sulfuric acid aqueous solution, adding alcohol into the resultant solution and selectively crystallizing sulfate of the rare earth element. Furthermore, Japanese Patent Laying-Open No. 09-157769 (which will be hereinafter referred to as PTD 2) discloses a method of recovering a rare earth element by hydrotreating and pulverizing alloy scraps containing a rare earth element, overheating the pulverized scraps to achieve an oxide, which is then brought into contact with an acid solution, to elute the rare earth element as ions into the acid solution and produce a deposit containing the rare earth element from this ion-containing acid solution.
Furthermore, Japanese Patent Laying-Open No. 2002-60855 (which will be hereinafter referred to as PTD 3) discloses a method of recycling neodymium (Nd)-based rare-earth magnet scraps by introducing the scraps into a molten-salt electrolytic bath including rare earth oxides as raw materials, melting the scraps in the electrolytic bath, separating the scraps into a rare earth oxide and a magnet alloy portion, reducing the rare earth oxide dissolved in the electrolytic bath to a rare earth metal by electrolysis, and alloying the magnet alloy portion and the rare earth metal, thereby reproducing the scraps as a rare earth metal. Furthermore, Japanese Patent Laying-Open No. 2002-198104 (which will be hereinafter referred to as PTD 4) discloses a method of recycling a hydrogen absorbing alloy, by which a hydrogen absorbing alloy is immersed as an anode in molten salt together with a cathode, in which state a voltage is applied between the cathode and the anode, to dissolve a rare earth element from the anode into the molten salt, thereby depositing a rare earth element on the surface of the cathode from the molten salt by an electrolytic reduction reaction, and recovering the rare earth element.
Furthermore, Japanese Patent Laying-Open No. 2003-73754 (which will be hereinafter referred to as PTD 5) discloses a method of recovering a rare earth element, by which a substance containing a rare earth element and an iron group element (for example, scraps of a rare-earth magnet and the like) into contact with iron chloride in a gaseous state or a molten state, causing a chloride reaction of the rare earth element in the substance to progress while keeping the iron group element in the substance in a metal state, and selectively recovering the rare earth element as chloride from the substance. Furthermore, Japanese Patent Laying-Open No. 2005-264209 (which will be hereinafter referred to as PTD 6) discloses a method of recovering a rare earth element through electrophoresis conducted in the state where the rare earth element is dissolved in molten salt having a prescribed composition. Furthermore, Japanese Patent Laying-Open No. 2009-287119 (which will be hereinafter referred to as PTD 7) discloses a method of recovering a rare earth element, by which a bipolar electrode-type diaphragm is disposed between a cathode and an anode during molten salt electrolysis to form a cathode chamber and an anode chamber, and a voltage is applied between the cathode and the anode while supplying rare earth element ions toward the anode chamber, to cause the rare earth element to diffuse and transmit through the diaphragm, thereby depositing the rare earth element on the surface of the cathode.